The present invention relates to the imaging arts. It finds particular application in conjunction with low and high-density cell detection in blood smears, biological assays, and the like, and will be described with particular reference thereto. However, it is to be appreciated that the present invention will also find application in imaging other types of low- or high-density features on various substantially planar surfaces and samples, such as imaging semiconductor wafers, imaging particulate contaminants in fluids or thin solid films, and so forth, with such imaging finding specific uses in the printing arts, electronic arts, medical arts, and other scientific and engineering areas.
With particular attention to cell detection, it has been determined by the inventors that a beneficial aspect to which the present application may be applied is to scan a large number of cells, such as 1 to 10 million cells, at a time. Thereafter, the concepts of the application may be used to identify either a small number of these cells, such as rare cells found in cancer, etc., or to be able to characterize each one of the scanned cells for use in research applications.
Clinical prenatal care benefits from directly accessing fetal tissues. In conventional amniocentesis, amniotic fluid surrounding the fetus is directly accessed and drawn. The amniotic fluid includes fetal cells which are extracted for study. To reduce risk to the fetus, ultrasound monitoring is typically performed during the amniocentesis to ensure that the probe needle does not contact or interfere with the fetus, and the amniocentesis procedure is performed by skilled clinical personnel. Nonetheless, amniocentesis is known to increase the risk of miscarriage.
As an alternative to amniocentesis, rare fetal cells in the maternal bloodstream can be extracted. It is known in the prenatal medical arts that fetal cells cross the placental barrier and enter the maternal bloodstream. The concentration of fetal cells in the maternal bloodstream is typically on the order of one fetal cell for every one million maternal cells. Such “rare” fetal cells can be extracted by drawing maternal blood or by other fluid extraction. DNA analysis, fetal blood typing, or other clinical studies are performed on the rare fetal cells to provide information about the fetus. Unlike amniocentesis, extraction of rare fetal cells from the maternal bloodstream is isolated from the fetus and the womb, and the extraction can be performed by a broad range of medical personnel authorized to draw blood.
In the clinical oncology arts, it is recognized that cancerous cells are typically present in small concentrations in a cancer patient's bloodstream. In the case of deep malignant tumors which are inaccessible except by invasive surgery, rare cancerous cells extracted from blood or another body fluid provide a convenient and cost effective pathway for detecting a cancer, periodically monitoring cancer remission, and diagnosing a cancer type. Rare cell analysis targeting cancerous cells is a promising diagnostic and monitoring technique for many types of cancers, including breast, lung, colon, and prostate cancers.
In these and other rare cell studies, a problem arises because the concentration of the rare cells in the blood or other body fluid is typically very low. In a typical rare cell study, blood is processed to remove cells that that are not needed. Then a fluorescent material is applied that attaches to antibodies, which in turn selectively attach to a cell surface or cellular protein of the rare cells. The fluorescent material may be a fluorescent marker dye or any other suitable material which will identify the cells of interest. A blood smear treated in this manner, which may include the blood and/or components of the blood, is prepared and optically analyzed to identify rare cells of the targeted type. For statistical accuracy it is important to obtain as large a number of cells as required for a particular process, in some studies at least ten rare cells should be identified, requiring a sampling of at least ten million cells for a one-in-one million rare cell concentration. Such a blood smear typically occupies an area of about 100 cm2. It is to be understood, however, that this is simply one example and other numbers of cells may be required for statistical accuracy for a particular test or study.
Turning to research applications, the scanning of a large number of cells and the characterization of each of the scanned cells may also have substantial benefits. For example, a hundred different patches, each containing 10,000 cells, may be generated where each patch will receive a different protocol or process. Thereafter it may be useful to determine how each cell on a specific patch is affected by the protocol or process which it has undergone. One procedure of achieving such detection would be to apply a fluorescent material, and to identify those cells to which the material has become attached either to the cell's surface, cellular proteins or other portions of the cell.
A particular area of research which may benefit from the present concepts includes HIV research, where it is known the virus enters into a cell causing the cell to produce the viral protein on its membrane. However, the produced viral protein exists in very small amounts, and therefore it is difficult to detect affected cells with existing technology.
A problem with cell analysis is the use of conventional technology which have relatively small fields of view (FOV), such as microscopes. To overcome the FOV limitation, cell analyses often employ automated high-speed scanning which however produces substantial undesirable acceleration forces on the scanned stage.
Another problem in cell studies, for both high and low density situations, is that the fluorescence intensity produced by treated cells is low, around 1000–2000 flours (fluorescent molecules). A high numerical aperture for the light-collecting aperture is preferred in the optical analysis system to provide good light collection.
Yet another problem in the cell studies is resolution. For example, if a cell has a diameter of about ten microns, the optics for the cell analysis preferably provides a resolution of this order. However, achieving high resolution typically requires a reduced field of view and consequently results in a decreased scanning speed and increased required sampling time.
The present invention contemplates a new and improved apparatus and method which overcomes the above-referenced problems and others.